Abstract:

In order to assess the property of the Paleozoic shale gas reservoir in the south Anhui of Yangtze region, based on the scanning electron microscopy, high pressure mercury-injection, N₂ and CO₂ gas adsorption methods, the pore characteristics and structures of shale samples from the Paleozoic shales in the South Anhui were studied, and the controlling factors of pores development were discussed. The results show that the porosity and permeability of shale samples are low, and the microscopic pores mainly include inter-grain pores, floe pores, dissolution pores, matrix intergranular pores and organic pores, and the micro-nano scale pores are well developed in these shales. The main pore types in the Paleozoic shales are micropores and mesopores, which account for over 50%. The pore structure of shale is dominated by the parallel-plate pore, cylinder pore and mixed pore, and the average size is about 4.17-12.06 nm. The pore volume and specific surface area increase with the increasing of total organic carbon content (TOC). The porosity of shale reduces as the vitrinite reflectance (R_o) increases. The pore volume increases with the increasing of clay mineral content, but decreases with the increasing of brittle mineral content.

Key words: shale gas reservoir, pore characteristic, pore structure, controlling factor, Paleozoic shale, south Anhui